The arthritis is usually in older persons with less mobility, muscle and ligament strength.
So equal trauma may lead to even worse disruption and slower recovery.
Medial and lateral collateral ligament
cruciate ligaments
meniscus
are all at risk along with fractures of femur, tibia fibula patella.

In brief:
Everything

Enough trauma can fully disrupt a normal or arthritic knee.

The arthritis is usually in older persons with less mobility, muscle and ligament strength.
So equal trauma may lead to even worse disruption and slower recovery.
Medial and lateral collateral ligament
cruciate ligaments
meniscus
are all at risk along with fractures of femur, tibia fibula patella.
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